Conventionally, there is known a bifuel vehicle which switches between the use of gas fuel such as CNG (Compressed Natural Gas) and the use of liquid fuel in order to realize the low emission. For example, in Patent Reference-1, there is disclosed a technique which keeps the target torque set just before switching the fuel, at the time of switching the fuel from the gas fuel to gasoline, so that the passengers does not feel the big torque shock even when the fuel to be used is switched from the gas fuel to the gasoline. In Patent Reference-1, there is also disclosed a technique which gradually returns the setting element of the target torque to the torque characteristic by the gasoline as time passes.
Patent Reference-1: Japanese Patent Application Laid-open under No. 2008-014162